Lubricating composition

ABSTRACT

A lubricating composition comprising a base oil blend and one or more additives wherein the base oil blend comprises: a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92 wt % and comprising less than 10 ppm of sulphur; and a Fischer-Tropsch derived base oil. The lubricating composition of the present invention exhibits improved detergency and engine cleanliness properties.

FIELD OF THE INVENTION

The present invention relates to lubricating compositions, particularly to lubricating compositions which are useful as heavy duty diesel engine oils and passenger car motor oils and which have improved detergency properties.

BACKGROUND OF THE INVENTION

It is to be noted that, although the present invention has been explained below in relation to lubricating compositions for particular use as a heavy duty diesel engine oil or a passenger car motor oil, the present invention is not limited in any way to such oils. The present invention can be equally applied to lubricating compositions intended for other applications, such as hydraulic fluids and turbine oils. Heavy duty diesel engine oils formulated using conventionally refined API Group II base oils are known in the art. Unfortunately, such formulations often suffer from the problem of insufficient detergency performance at high temperatures. It would therefore be desirable to formulate a lubricating composition for use, in particular, as a heavy duty diesel engine oil or as a passenger car motor oil which has improved high temperature detergency performance, and consequently which provides improved engine cleanliness.

SUMMARY OF THE INVENTION

According to the present invention there is provided a lubricating composition comprising a base oil blend and one or more additives wherein the base oil blend comprises:

-   -   a distillate naphthenic base oil having a saturates content as         measured by 19368 of greater than 92% and comprising less than         10 ppm of sulphur; and     -   a Fischer-Tropsch derived base oil.

It has surprisingly been found that the lubricating composition of the present invention provides improved high temperature detergency performance.

According to another aspect of the present invention there is provided the use of a lubricating composition as described herein as a heavy duty diesel engine oil or a passenger car motor oil.

According to a further aspect of the present invention there is provided the use of a lubricating composition as described herein for providing improved detergency performance, in particular at high temperatures.

According to a further aspect of the present invention there is provided the use of a lubricating composition as described herein for providing improved engine cleanliness.

DETAILED DESCRIPTION OF THE INVENTION

A first essential component of the lubricating composition of the present invention is a base oil blend. The base oil blend comprises a distillate naphthenic base oil and a Fischer-Tropsch derived base oil.

The naphthenic base oil for use in the base oil blend is a distillate naphthenic base oil having a saturates content as measured by 19368 of greater than 92wt %, preferably greater than 95 wt %, and more preferably greater than 98 wt %. In addition, the naphthenic base oil for use herein comprises less than 10 ppm of sulphur, preferably less than 5 ppm of sulphur.

As used herein the term “distillate base oil” means a base oil that has had a high vacuum distillation separation processing step whereby the viscosity grade has been fixed by defining the initial and final boiling point of the distillate fraction, prior to or after the upgrading step (extraction or hydroprocessing).

The distillate naphthenic base oil used in the base oil blend is preferably present at a level of from 5 wt % to 50 wt %, more preferably at a level of from 10 wt % to 30 wt %, based on the weight of the lubricating composition.

The naphthenic base oils are distillate base oils from naphthenic vacuum distillates obtained by refinery processes starting from naphthenic mineral crude feeds (typically, mineral crude feeds having a TAN (Total Acid Number; ASTM D 664) value of above 0.5 mg KOH/g are naphthenic (high TAN) and below 0.5 mg KOH/g (low TAN) are paraffinic); no dewaxing step normally takes place in the preparation of naphthenic base oils (contrary to the preparation of a paraffinic base oil in which a dewaxing step is needed). Optionally a dewaxing step can be applied if the high TAN crude has some trace residual waxes.

Preferably, the distillate naphthenic base oil used in the base oil blend has an initial boiling point (true boiling point according to ASTM D 2887) of above 350° C., preferably above 370° C., more preferably above 500° C. Also, the distillate Naphthenic base oil preferably has an aromatic atomic content C_(A) (according to ASTM D 3238) of below 2 wt. % (for a paraffinic base oil this is typically above 2 wt. %).

Preferably, the distillate naphthenic base oil used in the base oil blend has a pour point of below −10° C., preferably below −15° C. (according to ASTM D 5950).

Further it is preferred that the distillate naphthenic base oil used in the base oil blend has a Viscosity Index (according to ASTM D 2270) of below 90, preferably below 70, more preferably below 40, even more preferably below 10.

Commercially available sources of distillate naphthenic base oils suitable for use in the base oil blend include those commercially available from PetroChina (Karamay), e.g. under the trade designations “KN4006”, “KN4008”, “KN4010”, “KN4012”,“KN4016” and “KN6025” (known as “K series” naphthenic base oils).

There are no particular limitations regarding the Fischer-Tropsch derived base oil used in the base oil blend in the compositions according to the present invention. Preferably, the Fischer-Tropsch derived base oil used in the base oil blend is a Fischer-Tropsch derived distillate base oil.

Fischer-Tropsch derived base oils are known in the art. By the term “Fischer-Tropsch derived” is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil in the functional fluid compositions of the present invention are those as for example disclosed in EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO 00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166.

The Fischer-Tropsch derived base oil for use in the base oil blend is preferably present at a level of from 10 wt % to 70 wt %, more preferably from 20 wt % to 70 wt %, even more preferably from 30 wt % to 65 wt %, by weight of the lubricating composition.

Typically, the Fischer-Tropsch derived base oil used in the present invention has a kinematic viscosity at 100° C. (according to ASTM D 445) in the range of from 2.0 mm²/s to 35.0 mm²/s, preferably in the range of from 2 mm²/s to 25.0 mm²/s, more preferably in the range of from 2.5 mm²/s to 14 mm²/s. According to one aspect of the present invention the Fischer-Tropsch derived base oil preferably has a kinematic viscosity at 100° C. of at least 3.0 mm²/s (according to ASTM D445), preferably at least 4.0 mm²/s. According to another aspect of the present invention the Fischer-Tropsch derived base oil preferably has a kinematic viscosity at 100° C. of at least 7.0 mm²/s. In the event the Fischer-Tropsch base oil contains a blend of two or more base oils, it is preferred that the total contribution of the base oil to this kinematic viscosity is as indicated (from 2.0 to 35.0 mm²/s, preferably 2.0 to 25.0 mm²/s at 100° C. according to ASTM D 445, etc.).

In preferred embodiments of the present invention, the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil in the base oil blend is preferably in the range of from 10:90 to 50:50, more preferably in the range of from 10:90 to 40:60 and especially in the range of from 10:90 to 30:70.

It is preferred that the base oil blend (comprising a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92wt % and less than 10 ppm of sulphur and a Fischer-Tropsch base oil) has a pour point of less than −24° C. (according to ASTM D 5950), preferably less than −30° C. It is also preferred that the base oil blend (comprising a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92wt % and less than lOppm of sulphur and a Fischer-Tropsch base oil) has a Viscosity Index (according to ASTM D 2270) of greater than 95, preferably greater than 100. Further it is preferable that the base oil blend (comprising a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92wt % and less than 10 ppm of sulphur and a Fischer-Tropsch base oil) has a kinematic viscosity at 100° C. in the range of from 2.5 mm²/s to 35 mm²/s, more preferably in the range of from 2.5 mm²/s to 25 mm²/s, even more preferably in the range of from 3.5 mm²/s to 13 mm²/s.

The lubricating composition according to the present invention may, in addition to the base oil blend described above, additionally contain mixtures of one or more other mineral oils and/or one or more synthetic oils. Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

Suitable additional base oils for use in the lubricating oil composition of the present invention are Group I-III mineral base oils, Group IV poly-alpha olefins (PAOs) and mixtures thereof.

By “Group I”, “Group II”, “Group III” and “Group IV” base oils in the present invention are meant lubricating oil base oils according to the definitions of American Petroleum Institute (API) for category I, II, III and IV. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

Synthetic oils include hydrocarbon oils such as olefin oligomers (including polyalphaolefin base oils; PAOs), dibasic acid esters, polyol esters, polyalkylene glycols (PAGs), alkyl naphthalenes and dewaxed waxy isomerates. Synthetic hydrocarbon base oils sold by the Shell Group under the designation “Shell XHVI” (trade mark) may be conveniently used.

Preferably, the lubricating composition comprises from 1 wt % to 20 wt %, preferably from 2 wt % to 15 wt % of a naphthenic bright stock base oil, based on the total weight of the composition. A suitable naphthenic bright stock base oil is that commercially available under the tradename HVI H150 BSM from PetroChina having a kinematic viscosity at 100° C. (ASTM D445) of approximately 31 cSt.

The total amount of base oil (i.e. the base oil blend comprising a distillate naphthenic base oil having a saturates content as measured by 19368 of greater than 92% and comprising less than 10 ppm of sulphur and a Fischer-Tropsch derived base oil, as well as any base oils in addition to the base oil blend) incorporated in the lubricating composition of the present invention is preferably in the range of from 50 to 99.9 wt. %, more preferably in the range of from 70 to 98 wt. % and most preferably in the range of from 80 to 96 wt. %, based on the total weight of the lubricating composition.

The lubricating composition according to the present invention preferably has a Viscosity Index (according to ASTM D 2270) of above 95, more preferably above 100.

Further it is preferred that the composition has a Total Base Number (TBN) value (according to ASTM D 4739) of above 8 and below 75 mg KOH/g, preferably between 10 and 70 mg KOH/g.

The lubricating composition according to the present invention may further comprise one or more additives such as anti-oxidants, anti-wear additives, (preferably ashless) dispersants, detergents, extreme-pressure additives, friction modifiers, metal deactivators, corrosion inhibitors, demulsifiers, anti-foam agents, seal compatibility agents and additive diluent base oils, etc.

As the person skilled in the art is familiar with the above and other additives, these are not further discussed here in detail. Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526.

The lubricating compositions of the present invention may be conveniently prepared by admixing the one or more additives with the base oil(s).

The above-mentioned additives are typically present in an amount in the range of from 0.01 to 35.0 wt. %, based on the total weight of the lubricating composition, preferably in an amount in the range of from 0.05 to 25.0 wt. %, more preferably from 1.0 to 20.0 wt. %, based on the total weight of the lubricating composition.

Preferably the lubricating composition according to the present invention is a heavy duty diesel engine oil or a passenger car motor oil.

In one embodiment of the present invention, the lubricating composition herein is an SAE 15W-XX grade lubricating composition according to SAE J-300 wherein XX is selected from 20, 30, 40 and 50. In a preferred embodiment herein the lubricating composition is an SAE 15W-40 grade lubricating composition according to SAE J-300.

In another embodiment of the present invention the lubricating composition is an SAE 10W-YY grade lubricating composition according to SAE J-300 wherein YY is selected from 30 and 40.

The lubricating composition of the present invention has improved detergency and engine cleanliness properties. In particular, the lubricating composition of the present invention preferably exhibits a value of greater than 7 merits in the Komatsu Hot Tube Test carried out at 280° C. (Japanese Industrial Standards (JIS)—JIS method no. JPI-5S-55-99).

In another aspect, the present invention provides the use of a lubricating composition according to the present invention in order to improve detergency properties, in particular according to the Komatsu Hot Tube Test (Japanese Industrial Standards (JIS)—JIS method no. JPI-5S-55-99).

The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

EXAMPLES

Various lubricating compositions for use as SAE 15W-40 Heavy Duty Diesel Engine Oils (HDDEOs) (meeting the so-called SAE J300 Specifications as revised in January 2009; SAE stands for Society of Automotive Engineers) were formulated.

Table 1 indicates the properties for the base oils used. Table 2 indicates the composition and properties of the fully formulated Heavy Duty Diesel Engine Oils that were tested. The amounts of the components are given in wt. %, based on the total weight of the compositions.

All tested Heavy Duty Diesel Engine Oils contained a combination of a base oil blend and an additive package (which additive package was the same in all tested compositions), in addition to a Viscosity Modifier and a pour point depressant.

The “Additive package” was a special performance package for Heavy Duty Diesel Engine Oils and contained a combination of performance additives including over-based detergent, ashless dispersant, zinc anti-wear agent, anti-oxidant, and anti-foam agent.

“Base oil 1” was a naphthenic base oil commercially available from PetroChina (Karamay, China) under the trade designation “KN4010”.

“Base oil 2” was a Fischer-Tropsch derived base oil (“GTL 4”) having a kinematic viscosity at 100° C. (ASTM D445) of approx. 4 cSt (1 cSt corresponds to 1 mm²s⁻¹) GTL 4 may be conveniently manufactured by or similar to the process described in e.g. WO 02/070631, the teaching of which is hereby incorporated by reference.

“Base oil 3” was a PetroChina naphthenic brightstock termed HVI H150 BSM having a kinematic viscosity at 100° C. (ASTM D445) of approx. 31 cSt. “Base oil 4” was a GTL 8 cSt base oil having a having a kinematic viscosity at 100° C. (ASTM D445) of approx. 8 cSt.

“Base oil 5” was a commercially available API Group II base oil of mineral origin sold by Motiva Enterprises LLC, Tx, USA under the trade name Motiva Star 6.

“Base oil 6” was a commercially available API Group II base oil of mineral origin sold by Formosa Plastic Group, Mailiao, Taiwan under the trade name Formosa 500N.

“Base oil 7” was a commercially available API Group II base oil of mineral origin sold by Formosa Plastic Group, Mailiao, Taiwan under the trade name Formosa 150N.

The compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were obtained by mixing the base oils with the additive package using conventional lubricant blending procedures.

TABLE 1 Base oil 1 (KN4010 naphthenic Base oil 2 Base oil 3 Base oil 4 Base oil 5 Base oil 6 Base oil 7 base oil) (GTL 4) (HVIH150BSM) (GTL-8) (Motiva Star 6) (Formosa 500) (Formosa 150) Kinematic 10.22 4.102 30.69 7.616 6.551 11.05 5.203 viscosity at 100° C.¹ [cSt] Kinematic 150.8 17.99 539 43.71 42.76 98.21 28.17 viscosity at 40° C.¹ [cSt] VI Index² 4 132 84 143 104 97 116 Pour point³ −27 −33 −27 −24 −12 −18 −21 [° C.] Saturates⁴ 94.7 99.4 98.5 99.1 97.8 99.3 99.2 % weight Sulphur 4.9 <3 11.7 <3 — <3 <3 content⁵ ppm ¹According to ASTM D 445 ²According to ASTM D 2270 ³According to ASTM D 5950 ⁴According to IP 368 ⁵According to ASTM D2622

TABLE 2 Component Comp. Comp. [wt. %] Example 1 Example 2 Ex. 1 Ex. 2 Base oil 1 21.72 15.74 — — [KN4010] Base oil 2 25.5 — — — [GTL 4] Base oil 3 11.96 3.94 — — [HVI H150BSM] Base oil 4 19.52 59.02 — — [GTL 8] Base oil 5 — — — 78.7 [Motiva Star 6] Base oil 6 — — 15 — [Formosa 500] Base oil 7 — — 63.7 — [Formosa 150] Additive package 14.7 14.7 14.7 14.7 Viscosity Modifier 6.3 6.3 6.3 6.3 Pour Point Depressant 0.3 0.3 0.3 0.3 TOTAL 100 100 100 100 Kinematic viscosity 15.15 15.91 12.76 14.15 at 100° C.¹ [cSt] VdCCS-20 Celcius² mPa · s 6446 5786 3833 6706 VdCCS-25 Celcius² mPa · s — — 7127 — ¹According to ASTM D 445 ²Dynamic Viscosity (Cold Crank Simulator) according to ASTM D 5293

Detergency Performance

In order to demonstrate the detergency properties of the compositions according to the present invention, detergency measurements were performed according to the industry standard Komatsu Hot Tube Test (at 280° C. and 290° C.) (Japanese Industrial Standards (JIS)—JIS method no. JP1-5S-55-99). The measured values (in merits) are indicated in Table 3 below. For the test carried out at 280° C. a pass was deemed to be a value of greater than 7 merits, while a fail was deemed to be a value of 7 merits or less. For the test carried out at 290° C. a pass was deemed to be a value of greater than 6 merits, while a fail was deemed to be a value of 6 merits or less. Two merit measurements were taken for each example at each temperature (designated as “Merit 1” and “Merit 2” in Table 3 below).

Further the amount of deposits was also measured for each example, again according to the industry standard Komatsu Hot Tube Test (Japanese Industrial Standards (JIS)- JIS method no. JPI-5S-55-99). The amount of deposits measured in each example is shown below in Table 3.

TABLE 3 Comp. Comp. Example 1 Example 2 Ex. 1 Ex. 2 Results @ 280° C. 7.0/7.5 9.0/9.0 6.0/6.0 6.0/6.0 Merit 1/Merit 2 Average Merit at 7.3 9.0 6.0 6.0 280° C. PASS/FAIL at PASS PASS FAIL FAIL 280° C. (PASS = >7 merits (JASO) Results @ 290° C. 3.0/3.5 0.5/0.5 1.0/1.0 1.0/1.0 Merit 1/Merit 2 Average Merit at 3.3 0.5 1.0 1.0 290° C. PASS/FAIL at FAIL FAIL FAIL FAIL 290° C. (PASS = >6 merits (KES-EO DH) Deposits: 0.5/1.5 0/0 1.4/0.2 1.5/0.7 Results at 280° C. Weight 1 (mg)/Weight 2 (mg) Average weight 1 0 0.8 1.1 of deposits at 280° C. (mg) Deposits: 3.7/4.0 2.1/3.0 2.9/4.5 4.7/4.4 Results at 290° C. Weight 1 (mg)/Weight 2 (mg) Average weight 3.8 2.6 3.7 4.6 of deposits at 290° C. (mg)

Discussion

As can be learned from Table 3, it has been surprisingly found that the HDDEO composition according to the present invention (Examples 1 and 2) had improved detergency performance in the Komatsu Hot Tube Test compared to the HDDEO compositions based on normal mineral API Group II base oils (Comparative Examples 1-2 which contained the same additive, Viscosity Modifier and pour point depressant, in the same amounts, as the formulations of Examples 1 and 2). In particular, in the Komatsu Hot Tube Test carried out at 280° C., Example 1 had an average cleaniless merit of 7.3 (i.e. obtaining a “pass” in the test) and Example 2 had an average cleaniless merit of 9.0 (i.e. obtaining a “pass” in the test) while Comparative Examples 1 and 2 both had an average cleanliness merit of 6.0 (thereby obtaining a “fail” in the test). In the Komatsu Hot Tube Test carried out at 290° C., while Example 1 obtained a “fail” in the test, it obtained a higher average cleaniless merit than those of Comparative Examples 1 and 2, indicating improved detergency performance for the composition of Example 1.

Turning to the deposits results, at 280° C. and 290° C. Example 2 exhibited significantly reduced deposits compared to Comparative Examples 1 and 2 indicating improved detergency performance for Example 2. 

1. A lubricating composition comprising a base oil blend and one or more additives wherein the base oil blend comprises: a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92wt % and comprising less than 10 ppm of sulphur; and a Fischer-Tropsch derived base oil.
 2. A lubricating composition according to claim 1 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 50:50.
 3. A lubricating composition according to claim 1 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 40:60.
 4. A lubricating composition according to claim 1 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 30:70.
 5. A lubricating composition according to claim 1 wherein the base oil blend has a pour point of less than -24° C. (according to ASTM D 5950).
 6. A lubricating composition according to claim 1 wherein the base oil blend has a Viscosity Index (according to ASTM D 2270) of greater than
 95. 7. A lubricating composition according to claim 1 wherein the base oil blend has a kinematic viscosity at 100° C. in the range of from 2.5 mm²/s to 35 mm²/s (according to ASTM D445).
 8. A lubricating composition according to claim 1 wherein the Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. in the range of from 2.5 mm²/s to 14 mm²/s (according to ASTM D445).
 9. A lubricating composition according to claim 1 wherein the lubricating composition has a value of greater than 7 merits in the Komatsu Hot Tube Test carried out at 280° C.
 10. A lubricating composition according to claim 1 wherein the lubricating composition is an SAE 15W-XX grade lubricating composition according to SAE J-300 wherein XX is selected from 20, 30, 40 and
 50. 11. A lubricating composition according to claim 10 wherein the lubricating composition is an SAE 15W-40 grade lubricating composition according to SAE J-300.
 12. A lubricating composition according to claim 1 wherein the lubricating composition is an SAE 10W-YY grade lubricating composition according to SAE J-300 wherein YY is selected from 30 and
 40. 13. (canceled)
 14. (canceled)
 15. (canceled)
 16. A method comprising lubricating an engine with a lubricating composition that comprises a base oil blend and one or more additives, wherein the base oil blend comprises: a distillate naphthenic base oil having a saturates content as measured by IP368 of greater than 92wt % and comprising less than 10 ppm of sulphur; and a Fischer-Tropsch derived base oil.
 17. A method according to claim 16 wherein the engine is a heavy duty diesel engine.
 18. A method according to claim 16 wherein the engine is a passenger car engine.
 19. A method according to claim 16 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 50:50.
 20. A method according to claim 16 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 40:60.
 21. A method according to claim 16 wherein the weight ratio of the distillate naphthenic base oil to the Fischer-Tropsch derived base oil is in the range of from 10:90 to 30:70.
 22. A method according to claim 16 wherein the base oil blend has a pour point of less than −24° C. (according to ASTM D 5950).
 23. A method according to claim 16 wherein the base oil blend has a Viscosity Index (according to ASTM D 2270) of greater than
 95. 